JP2013141068A - Piezoelectric device and frequency adjustment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress frequency variation immediately after a start-up.SOLUTION: A piezoelectric device of an embodiment includes a piezoelectric element, an oscillation circuit, a correction voltage generating circuit, and a synthesis circuit. The oscillation circuit adjusts a resonance frequency of the piezoelectric element in accordance with a control voltage. The correction voltage generating circuit generates a correction voltage on the basis of an input integral value of a power source voltage. The synthesis circuit outputs the control voltage combined with the correction voltage to the oscillation circuit.

Description

  The disclosed embodiments relate to a piezoelectric device and a frequency adjustment method.

  Conventionally, as a piezoelectric device used as a signal source such as a reference signal source or a clock signal source, a voltage control type piezoelectric device that controls the resonance frequency of a piezoelectric element with an external voltage is known.

  Patent Document 1 discloses a technique related to a VCTCXO (Voltage Controlled Temperature Compensated Crystal Oscillator) which is a kind of voltage controlled piezoelectric device. Specifically, Patent Document 1 discloses a correction voltage obtained by passing a power supply voltage through a differentiating circuit in order to suppress frequency fluctuations caused by a deviation between the temperature of the piezoelectric element immediately after power-on and the temperature detected by the temperature sensor. A technique for correcting the temperature compensation voltage by using it is disclosed.

  That is, when the power is turned on, the power supply voltage input to the differentiating circuit changes, so that a correction voltage corresponding to the change is output from the differentiating circuit. In the technique described in Patent Document 1, frequency correction at startup is suppressed by correcting the temperature compensation voltage using this correction voltage.

JP 2008-271355 A

  However, the above-described conventional technology does not consider the rise characteristic of the power supply voltage. For this reason, the above-described conventional technology has room for further improvement in terms of suppressing frequency fluctuations immediately after startup.

  An object of one embodiment is to provide a piezoelectric device and a frequency adjustment method capable of suppressing frequency fluctuations immediately after startup.

  A piezoelectric device according to one aspect of an embodiment includes a piezoelectric element, an oscillation circuit, a correction voltage generation circuit, and a control voltage output circuit. The oscillation circuit adjusts the resonance frequency of the piezoelectric element according to the control voltage. When the power supply voltage is input, the correction voltage generation circuit generates a correction voltage based on the integrated value of the input power supply voltage. The control voltage output circuit outputs a control voltage obtained by synthesizing the correction voltage to the oscillation circuit.

  According to one aspect of the embodiment, it is possible to suppress frequency fluctuations immediately after startup.

FIG. 1 is an explanatory view of the piezoelectric device according to the present embodiment in a cross-sectional view. FIG. 2 is a diagram showing a configuration of the integrated circuit element. FIG. 3 is a diagram illustrating a configuration of the correction voltage generation circuit. FIG. 4A is a diagram illustrating the time change of the power supply voltage input to the variable resistor. FIG. 4B is a diagram illustrating time variation of the integrated value of the power supply voltage. FIG. 4C is a diagram illustrating the time variation of the correction voltage. FIG. 5 is a diagram illustrating time variation of the coefficient value of the RC integrating circuit and the coefficient value of the CR differentiating circuit. FIG. 6 is a diagram illustrating the rising characteristics of the power supply voltage. FIG. 7 is a diagram exemplifying a change with time of the correction voltage obtained by passing the power supply voltages of the power supply 1, the power supply 2 and the ideal power supply shown in FIG. 6 through the CR differentiation circuit. FIG. 8 is a diagram illustrating the time variation of the correction voltage obtained by passing the power supply voltages of the power supply 1, the power supply 2 and the ideal power supply shown in FIG. 6 through the RC integration circuit. FIG. 9 is a diagram illustrating time variation of the voltage difference between the correction voltage of the power source 1 and the correction voltage of the power source 2.

  Hereinafter, embodiments of a piezoelectric device and a frequency adjustment method disclosed in the present application will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

  FIG. 1 is an explanatory view of the piezoelectric device according to the present embodiment in a cross-sectional view. As shown in FIG. 1, the piezoelectric device 1 according to the present embodiment includes a package 10, a piezoelectric element 20, a lid 30, and an integrated circuit element 40.

  In the following description, the surface on the side where the integrated circuit element 40 is provided as viewed from the package 10 is referred to as the “lower surface” of the piezoelectric device 1, and the surface on the side where the lid 30 is provided is referred to as the “upper surface”. In the following description, “lower surface” or “upper surface” may be referred to as “main surface”.

  The package 10 is an H-shaped container body in which concave portions (hereinafter referred to as “cavities”) are formed on the upper surface side and the lower surface side, respectively. The piezoelectric element 20 is disposed in the upper surface side cavity of the package 10, and the integrated circuit element 40 is disposed in the lower surface side cavity.

  A metallized layer 51 is provided on the top surface of the package 10. The metallized layer 51 is used when a lid 30 described later is joined to the package 10. An external connection terminal 52 is provided on the lowermost surface of the package 10. The external connection terminal 52 is a terminal for connecting the piezoelectric device 1 to an electronic device such as a portable terminal device.

  The piezoelectric element 20 is connected to the connection pad 53 via the conductive adhesive 54. The connection pad 53 is a pad that electrically connects the piezoelectric element 20 to the integrated circuit element 40 and is provided on the bottom surface of the upper surface side cavity. The connection pad 53 is electrically connected to the connection pad 56 on the integrated circuit element 40 side through the internal wiring 57.

  The piezoelectric element 20 is a crystal element in which excitation electrodes are arranged on both main surfaces of a crystal piece formed in a plate shape, for example. The excitation electrode is provided with a pair of extraction electrodes drawn out toward the end of the crystal piece, and the extraction electrodes and the connection pads 53 are connected via the conductive adhesive 54, so that the piezoelectric electrodes are connected. The element 20 is electrically connected to the connection pad 53.

  Here, a case where the crystal piece of the piezoelectric element 20 is formed with a cut angle that is an AT cut will be described, but the cut angle of the crystal piece may be a cut angle other than the AT cut. Further, the piezoelectric element 20 may have a shape other than a plate shape.

  The lid 30 is a member that closes the upper surface side cavity. Specifically, the lid body 30 is configured such that the sealing material layer 55 provided on the lower surface of the lid body 30 and the metallized layer 51 provided on the uppermost surface of the package 10 are overlapped with each other. Placed on. Thereafter, the sealing material layer 55 and the metallized layer 51 are joined by seam welding or the like, whereby the upper surface side cavity is hermetically sealed.

  The integrated circuit element 40 controls the oscillation operation of the piezoelectric element 20. The integrated circuit element 40 is connected to the package 10 via connection pads 56 provided on the upper surface of the lower surface side cavity of the package 10.

  The connection pad 56 is a pad that electrically connects the integrated circuit element 40 to the piezoelectric element 20. Specifically, the connection pad 56 is electrically connected to the connection pad 53 of the piezoelectric element 20 via an internal wiring 57 provided inside the package 10. A part of the connection pad 56 is connected to an external connection terminal 52 provided on the lowermost surface of the package 10 by an internal wiring (not shown) of the package 10.

  As described above, the piezoelectric element 20 and the integrated circuit element 40 are electrically connected via the connection pad 53, the conductive adhesive 54, the connection pad 56, and the internal wiring 57.

  Here, the integrated circuit element 40 is assumed to be connected to the package 10 via connection pads 56 provided in an array (so-called flip chip mounting). (For example, wire bonding) may be used.

  In addition, the space in the lower surface side cavity may be filled with a material such as a resin after the integrated circuit element 40 is mounted. As the resin used as the filler, for example, polyimide or epoxy resin can be used. Moreover, you may use the composition obtained by mixing additives and additives, such as a hardening | curing agent, with this epoxy resin.

  Next, the configuration of the integrated circuit element 40 will be described with reference to FIG. FIG. 2 is a diagram showing a configuration of the integrated circuit element 40. Note that FIG. 2 shows only main components from the viewpoint of making the description easy to understand.

  In the present embodiment, an example in which the package structure of the piezoelectric device 1 is a so-called H-type structure in which cavities are respectively formed on the upper surface side and the lower surface side will be described. It is not limited to the H-type structure.

  For example, as a package of the piezoelectric device 1, a first container body in which the piezoelectric element 20 is hermetically sealed and a second container body in which the integrated circuit element 40 is accommodated may be formed separately. In this case, the piezoelectric device 1 can be obtained by joining the first container body and the second container body. Further, a container having one cavity may be used as the package of the piezoelectric device 1.

  The piezoelectric device 1 may have a structure in which the package cavity is hermetically sealed using the integrated circuit element 40 instead of the lid. The piezoelectric device 1 may have a structure in which the integrated circuit element 40 is mounted in the cavity and the piezoelectric element 20 is disposed above the integrated circuit element 40.

  As shown in FIG. 2, the integrated circuit element 40 includes a terminal Vdd, a terminal Out, a terminal GND, a terminal TX1, and a terminal TX2. The integrated circuit element 40 includes an oscillation circuit 41, a temperature compensation unit 42, a correction voltage generation circuit 43, a memory 44, and a synthesis circuit 45. The integrated circuit element 40 includes a high frequency blocking resistor R1 and a buffer amplifier INV1.

  The terminal Vdd, the terminal Out, and the terminal GND are connected to the external connection terminal 52, respectively. An external power supply voltage is applied to the terminal Vdd via the external connection terminal 52. Although not shown here, the power supply voltage applied to the terminal Vdd is also input to the temperature compensation unit 42, the correction voltage generation circuit 43, and the like.

  From the terminal Out, a signal based on the oscillation signal is output to the outside via the external connection terminal 52. The terminal GND is connected to an external ground via the external connection terminal 52. The terminals TX1 and TX2 are connected to a pair of lead electrodes in the piezoelectric element 20.

  The oscillation circuit 41 oscillates the piezoelectric element 20 at a predetermined frequency and generates a signal corresponding to the resonance frequency of the piezoelectric element 20. Specifically, the oscillation circuit 41 includes an oscillation amplifier INV2, a feedback resistor R2, capacitors C1 and C2, and variable capacitance diodes Cv1 and Cv2.

  In the oscillation circuit 41, the oscillation amplifier INV2 amplifies the power supply voltage input via the terminal Vdd, and the feedback resistor R2 feeds back the amplified power supply voltage to the oscillation amplifier INV2, thereby oscillating the piezoelectric element 20. Let Further, in the oscillation circuit 41, the resonance voltage of the piezoelectric element 20 is adjusted by supplying the control voltage input from the synthesis circuit 45 via the high frequency blocking resistor R1 to the variable capacitance diodes Cv1 and Cv2.

  Thus, the oscillation circuit 41 adjusts the resonance frequency of the piezoelectric element 20 according to the control voltage. Capacitors C1 and C2 are DC blocking capacitors. The anode sides of the variable capacitance diodes Cv1 and Cv2 are connected to the ground via the terminal GND.

  The signal generated by the oscillation circuit 41 is input to the buffer amplifier INV1. The buffer amplifier INV1 is a CMOS inverter, for example, and amplifies the input signal and outputs it to the terminal Out.

  The temperature compensation unit 42 includes a temperature sensor 42a, a memory 42b, and a temperature compensation circuit 42c. The temperature sensor 42a is a sensor provided to detect the temperature of the piezoelectric element 20, and outputs the detected temperature information to the temperature compensation circuit 42c. The memory 42b stores temperature compensation data used when the temperature compensation circuit 42c performs temperature compensation.

  Here, the piezoelectric element 20 has a temperature characteristic in which the frequency deviation changes in a cubic function with respect to the temperature. The frequency deviation is an amount of deviation from the reference frequency. The reference frequency is a desired frequency in the piezoelectric device 1. In the memory 42b, for example, a coefficient of a cubic function that cancels the temperature characteristic of the piezoelectric element 20 is stored as temperature compensation data.

  The temperature compensation circuit 42c is a cubic function generating circuit, and uses the temperature information input from the temperature sensor 42a and the temperature compensation data read from the memory 42b to generate a compensation voltage derived from the cubic function. The compensation voltage generated by the temperature compensation circuit 42 c is input to the synthesis circuit 45. As described above, the piezoelectric device 1 according to this embodiment is a temperature-compensated oscillator including the temperature compensation unit 42.

  Here, when power is supplied to the piezoelectric device 1 and the integrated circuit element 40 is activated, the integrated circuit element 40 generates heat, and thereafter, the temperature of the piezoelectric element 20 rises as the integrated circuit element 40 generates heat. The temperature sensor 42 a is usually provided in the integrated circuit element 40 or in the vicinity of the integrated circuit element 40. For this reason, immediately after the power is turned on, a temperature higher than the actual temperature of the piezoelectric element 20 is detected by the temperature sensor 42a, and then the actual temperature of the piezoelectric element 20 approaches the detected temperature of the temperature sensor 42a.

  As a result, the temperature compensation unit 42 outputs a compensation voltage different from the appropriate compensation voltage. For this reason, if the compensation voltage from the temperature compensation unit 42 is used as a control voltage as it is, many times until the temperature of the piezoelectric element 20 and the detected temperature of the temperature sensor 42a match and the signal output from the oscillation circuit 41 becomes stable. It takes time.

  In recent years, for example, electronic devices equipped with a GPS (Global Positioning System) function have been required to shorten the time from startup to frequency stabilization, and it is important how to suppress frequency fluctuations immediately after startup. It is a difficult issue.

  Therefore, the piezoelectric device 1 according to the present embodiment supplies the control voltage obtained by synthesizing the correction voltage generated by the correction voltage generation circuit 43 to the compensation voltage generated by the temperature compensation unit 42 to the oscillation circuit 41. input. Thereby, the frequency fluctuation immediately after starting can be suppressed.

  Further, the piezoelectric device 1 according to the present embodiment uses an integration circuit as the correction voltage generation circuit 43. Thereby, unlike the case where a differentiation circuit is used, it is possible to perform correction in consideration of the rising characteristic of the power supply voltage, and it is possible to further suppress the frequency fluctuation immediately after the start-up. Below, these points are demonstrated concretely.

  The correction voltage generation circuit 43 is a circuit that generates a correction voltage for correcting the compensation voltage generated by the temperature compensation unit 42. Specifically, the correction voltage generation circuit 43 includes an integration circuit, and generates a correction voltage based on the integrated value of the input power supply voltage. The correction voltage generated by the correction voltage generation circuit 43 is input to the synthesis circuit 45.

  The memory 44 stores correction data used when the correction voltage generation circuit 43 generates a correction voltage. Here, an amplitude select code and a time constant select code are stored as correction data. The amplitude select code and the time constant select code are determined based on measurement results obtained by actually measuring the fluctuation (drift characteristic) of the frequency deviation of the piezoelectric element 20 from the startup to the stabilization of the frequency.

  As the memory 42b and the memory 44, nonvolatile memories such as PROM (Programmable Read Only Memory) and EEPROM (Electrical Erasable Programmable Read Only Memory) can be used.

  The synthesis circuit 45 is an operational amplifier, for example, and generates a control voltage by synthesizing the compensation voltage input from the temperature compensation unit 42 and the correction voltage input from the correction voltage generation circuit 43. The control voltage generated by the synthesis circuit 45 is input to the oscillation circuit 41 via the high frequency blocking resistor R1. Thus, the synthesis circuit 45 is an example of a control voltage output circuit that outputs a control voltage obtained by synthesizing the correction voltage to the oscillation circuit 41.

  Next, the configuration of the correction voltage generation circuit 43 will be described with reference to FIG. FIG. 3 is a diagram illustrating a configuration of the correction voltage generation circuit 43.

  As shown in FIG. 3, the correction voltage generation circuit 43 includes a terminal Vdd, a terminal Vh, and a terminal GND. The correction voltage generation circuit 43 includes a voltage dividing circuit 43a, a buffer amplifier 43b, a variable resistor 43c, an inverting circuit 43d, and a capacitor C3.

  An external power supply voltage is applied to the terminal Vdd via the terminal Vdd (see FIG. 2) of the integrated circuit element 40. The power supply voltage applied to the terminal Vdd is input to the voltage dividing circuit 43a.

  A correction voltage is output from the terminal Vh. The correction voltage output from the terminal Vh is input to the synthesis circuit 45. The terminal GND is connected to an external ground via the terminal GND of the integrated circuit element 40. The voltage dividing circuit 43a and the capacitor C3 are connected to the terminal GND.

  The voltage dividing circuit 43a generates a voltage proportional to the input power supply voltage. The voltage division by the voltage dividing circuit 43 a is determined by the amplitude select code stored in the memory 44. The power supply voltage divided by the voltage dividing circuit 43a is input to the variable resistor 43c via the buffer amplifier 43b for preventing noise.

  The variable resistor 43c is a resistor having a variable resistance value. The resistance value of the variable resistor 43 c is determined by a time constant select code stored in the memory 44. A capacitor C3 is connected to the subsequent stage of the variable resistor 43c.

  As described above, the correction voltage generation circuit 43 includes an RC integration circuit in which the variable resistor 43c and the capacitor C3 are connected in series. In this RC integration circuit, the time constant is determined by the time constant select code, and a voltage having a waveform equal to the time integration of the input power supply voltage is generated.

  The inverting circuit 43d inverts the waveform of the integral value of the power supply voltage input from the connection point between the variable resistor 43c and the capacitor C3, and outputs the correction voltage obtained thereby to the synthesis circuit 45 via the terminal Vh. For example, an operational amplifier or a CMOS inverter can be used as the inverting circuit 43d.

  Here, the waveform of the integral value of the power supply voltage output from the RC integration circuit and the waveform of the correction voltage output from the inverting circuit 43d will be described with reference to FIGS. 4A to 4C. FIG. 4A is a diagram illustrating the time variation of the power supply voltage input to the variable resistor 43c, FIG. 4B is a diagram illustrating the time variation of the integrated value of the power supply voltage, and FIG. 4C is the time of the correction voltage. It is a figure which illustrates change.

  FIG. 4A shows an ideal example in which the power supply voltage immediately rises to the specified voltage V1 immediately after the power is turned on. The power supply voltage actually requires a predetermined time to reach the specified voltage V1, but this point will be described later.

  The RC integrating circuit delays the input power supply voltage by a time determined by the time constant and outputs the delayed power supply voltage. For this reason, as shown in FIG. 4B, the RC integration circuit outputs a waveform in which the rise of the power supply voltage shown in FIG. 4A is smoothed.

  Further, the inverting circuit 43d inverts the output waveform from the RC integrating circuit with reference to the voltage V1 / 2. As a result, as shown in FIG. 4C, the inverting circuit 43d outputs a waveform that becomes the voltage V1 immediately after the power is turned on, and then gradually attenuates toward the voltage 0.

  The piezoelectric device 1 uses a control voltage obtained by combining the correction voltage shown in FIG. 4C with the compensation voltage output from the temperature compensation unit 42. As a result, a compensation voltage deviation caused by a deviation between the temperature of the piezoelectric element 20 and the temperature detected by the temperature sensor 42a immediately after the power is turned on is corrected by the correction voltage, so that it is possible to suppress frequency fluctuations at the time of startup.

  Here, the waveform of the correction voltage shown in FIG. 4C is determined by the amplitude select code and the time constant select code stored in the memory 44. That is, the prescribed voltage V1 in the power supply voltage input to the variable resistor 43c is determined by the amplitude select code, and the resistance value of the variable resistor 43c is determined by the time constant select code, whereby the waveform of the correction voltage is determined.

  The amplitude select code and the time constant select code are respectively determined based on measurement results obtained by actually measuring the drift characteristics of the piezoelectric element 20 when the compensation voltage output from the temperature compensation unit 42 is used as a control voltage. The

  As described above, it is ideal that the power supply voltage immediately reaches the specified voltage immediately after the power is turned on, but actually, a predetermined time is required until the power supply voltage reaches the specified voltage.

  Here, the rise characteristic of the power supply voltage, that is, the temporal change until the power supply voltage reaches the specified voltage after the power is turned on differs depending on the power supply used. For this reason, the rising characteristic of the power supply voltage differs between the test power supply used when measuring the drift characteristics of the piezoelectric element 20 and the power supply connected to the piezoelectric device 1 after product shipment. Therefore, the amplitude select code and the time constant select code determined using the test power supply may not be suitable depending on the power supply connected to the piezoelectric device 1 after product shipment.

  However, the piezoelectric device 1 according to the present embodiment generates the correction voltage using the RC integration circuit, so that the amplitude selection code and the time constant selection are compared with the case where the correction voltage is generated using the CR differentiation circuit. The influence of the code shift can be reduced.

  Hereinafter, this point will be described with reference to FIG. FIG. 5 is a diagram illustrating time variation of the coefficient value of the RC integrating circuit and the coefficient value of the CR differentiating circuit. In FIG. 5, the coefficient value of the CR differentiation circuit is indicated by a solid line, and the coefficient value of the RC integration circuit is indicated by a dotted line.

  Assuming that the power supply voltage (V) is V0 and the correction voltage (V) is Vx, the relationship between the power supply voltage V0 and the correction voltage Vx when the power supply voltage is passed through the CR differentiating circuit to generate the correction voltage is Vx = V0 × It is expressed by exp (-T / RC). Here, T is time (s), R is a resistance value (Ω), and C is a capacitance value (F). RC is a time constant.

  Therefore, “exp (−T / RC)”, which is a coefficient value of the CR differentiating circuit, is 1 immediately after power-on, as shown in FIG. 5, and then decreases at a decreasing rate corresponding to the time constant RC. Go.

  On the other hand, the relationship between the power supply voltage V0 and the correction voltage Vx when the power supply voltage is passed through the RC integration circuit to generate the correction voltage is expressed by Vx = V0 × {1-exp (−T / RC)}. Therefore, the time change of the coefficient value “1-exp (−T / RC)” of the RC integration circuit is 0 immediately after power-on, as shown in FIG. 5, and thereafter, at an increasing rate according to the time constant RC. It will increase.

  Thus, in a predetermined time zone including immediately after power-on, the coefficient value of the RC integration circuit is smaller than the coefficient value of the CR differentiation circuit. The smaller the coefficient value is, the less influence the variation in the rising characteristic of the power supply voltage has on the correction voltage. Therefore, when the value of the time constant RC is not appropriate, the error generated in the correction voltage is more than the RC integration circuit than the CR differentiation circuit. Is smaller.

  That is, the piezoelectric device 1 reduces the influence of the variation in the rising characteristics on the correction voltage even if the rising characteristics of the test power supply are different from the rising characteristics of the power supply connected to the piezoelectric device 1 after product shipment. be able to. Therefore, according to the piezoelectric device 1, it is possible to further suppress the frequency fluctuation immediately after the start-up as compared with the case where the correction voltage is generated using the CR differentiation circuit.

  Next, a comparison between the case where the correction voltage is generated using the CR differentiation circuit and the case where the correction voltage is generated using the RC integration circuit will be described more specifically with reference to FIGS. FIG. 6 is a diagram illustrating the rising characteristics of the power supply voltage.

  Here, in FIG. 6, the rising characteristic of the power source (hereinafter referred to as “ideal power source”) in which the power source voltage immediately rises to the specified voltage immediately after the power is turned on is indicated by a thick solid line. In FIG. 6, the rising characteristic of the power supply 1 that rises relatively quickly to the specified voltage is indicated by a thin solid line, and the rising characteristic of the power supply 2 that rises slower than the power supply 1 is indicated by an alternate long and short dash line. .

  As shown in FIG. 6, the power supply voltage requires a predetermined time to reach the specified voltage. Further, the temporal change until the power supply voltage reaches the specified voltage, that is, the rising characteristic of the power supply voltage is different for each power supply.

  FIG. 7 is a diagram exemplifying a change with time of the correction voltage obtained by passing the power supply voltages of the power supply 1, the power supply 2 and the ideal power supply shown in FIG. 6 through the CR differentiation circuit. Hereinafter, the voltage output from the RC integration circuit, that is, the correction voltage before being inverted by the inverting circuit 43d is referred to as “correction voltage” for convenience.

  As shown in FIG. 7, for example, a large difference occurs between the correction voltage of the power supply 1 and the correction voltage of the power supply 2 at a time T after a predetermined time from turning on the power. The amount of frequency adjustment depends on the correction voltage. For this reason, when the correction voltage is generated using the CR differentiating circuit, a large difference occurs in the frequency adjustment amount due to the difference in the rising characteristics of the power supply voltage.

  FIG. 8 is a diagram illustrating the time variation of the correction voltage obtained by passing the power supply voltages of the power supply 1, the power supply 2 and the ideal power supply shown in FIG. 6 through the RC integration circuit.

  As shown in FIG. 8, when the RC integration circuit is used, the difference between the correction voltage of the power supply 1 and the correction voltage of the power supply 2 is smaller than that when the CR differentiation circuit is used. That is, it can be seen that when the RC integration circuit is used, even if there is a difference in the rising characteristics of the power supply voltage, there is no significant difference in the frequency adjustment amount.

  FIG. 9 is a diagram illustrating the time change of the voltage difference between the correction voltage of the power supply 1 and the correction voltage of the power supply 2 (correction voltage of the power supply 2−correction voltage of the power supply 1). In FIG. 9, the voltage difference when the CR differentiation circuit is used is indicated by a solid line, and the voltage difference when the RC integration circuit is used is indicated by a dotted line.

  As shown in FIG. 9, when the correction voltage is generated using the CR differentiating circuit, it can be seen that the correction voltage varies greatly due to the difference in the rising characteristics of the power supply voltage. In contrast, when the correction voltage is generated using the RC integration circuit, it can be seen that the variation in the correction voltage due to the difference in the rising characteristics of the power supply voltage is smaller than when the CR differentiation circuit is used.

  As described above, the piezoelectric device 1 can perform temperature compensation in consideration of the rising characteristic of the power supply voltage by using the RC integration circuit, and the frequency variation immediately after the start-up compared to the case of using the CR differentiation circuit. Can be further suppressed.

  As described above, the piezoelectric device 1 according to this embodiment includes the piezoelectric element 20, the oscillation circuit 41, the correction voltage generation circuit 43, and the synthesis circuit 45. The oscillation circuit 41 adjusts the resonance frequency of the piezoelectric element 20 according to the control voltage. The correction voltage generation circuit 43 generates a correction voltage based on the integrated value of the input power supply voltage. Further, the synthesis circuit 45 outputs a control voltage obtained by synthesizing the correction voltage to the oscillation circuit 41. Therefore, frequency fluctuations immediately after startup can be suppressed.

  In the above-described embodiment, an example in which the RC integration circuit is a series RC circuit formed by connecting a resistor and a capacitor in series has been described. However, the RC integration circuit includes a resistor and a capacitor in parallel. A parallel RC circuit formed by connection may be used. Further, in order to obtain a more stable integrated waveform, an integrating circuit further including an operational amplifier may be used.

  Further, the integrated circuit element 40 shown in FIG. 2 and the correction voltage generation circuit 43 shown in FIG. 3 do not necessarily need to be physically configured as shown. That is, the specific mode of distribution / integration of each component in the integrated circuit element 40 and the correction voltage generation circuit 43 is not limited to the illustrated one, and all or a part thereof is functionally or physically in an arbitrary unit. It can be configured to be distributed and integrated.

  Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications can be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

DESCRIPTION OF SYMBOLS 1 Piezoelectric device 10 Package 20 Piezoelectric element 30 Cover body 40 Integrated circuit element 41 Oscillation circuit 42 Temperature compensation part 42a Temperature sensor 42b Memory 42c Temperature compensation circuit 43 Correction voltage generation circuit 43a Voltage division circuit 43b Buffer amplifier 43c Variable resistance 43d Inversion circuit 44 Memory 45 Composite circuit 51 Metallized layer 52 External connection terminal 53 Connection pad 54 Conductive adhesive 55 Sealing material layer 56 Connection pad 57 Internal wiring

Claims (5)

A piezoelectric element;
An oscillation circuit for adjusting the resonance frequency of the piezoelectric element according to a control voltage;
A correction voltage generation circuit that generates a correction voltage based on an integral value of the input power supply voltage when the power supply voltage is input; and
And a control voltage output circuit that outputs the control voltage combined with the correction voltage to the oscillation circuit. The correction voltage generation circuit includes:
The piezoelectric device according to claim 1, further comprising an RC integration circuit in which a resistor and a capacitor are connected. The correction voltage generation circuit includes:
An inverting circuit for inverting the waveform of the integrated value of the power supply voltage,
The inverting circuit is
The piezoelectric device according to claim 1 or 2, wherein the integrated value after inversion is output to the control voltage output circuit as the correction voltage. A temperature compensation circuit for performing temperature compensation on the resonance frequency of the piezoelectric element;
The control voltage output circuit includes:
4. The piezoelectric device according to claim 1, wherein a combined voltage of the compensation voltage input from the temperature compensation circuit and the correction voltage is output to the oscillation circuit as the control voltage. 5. A generation step of generating a correction voltage based on an integrated value of the input power supply voltage when the power supply voltage is input;
An output step of outputting a control voltage obtained by synthesizing the correction voltage to an oscillation circuit;
An adjustment step in which the oscillation circuit adjusts a resonance frequency of the piezoelectric element according to the control voltage.

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